EMPLOYEE BENEFIT PLANS (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Apr. 30, 2022
Components of net periodic benefit cost:
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	$ 23,000,000	$ 259,300,000
Amortization of unrecognized prior service cost	(525,000)	(289,000)	$ 279,000
Amortization of net (gain) loss	$ (1,960,000)	$ (17,010,000)	$ (45,896,000)
DefinedBenefitPlanAssumptionsUsedToDetermineBenefitObligationsRateofCompensationIncreaseMinimum	4.30%	5.00%
Minimumnumberofyearsofserviceforcertainemployeestobeeligibletoparticipateinsharedwelfareplansthatprovidepostretirementmedicalandlifeinsurancebenefits		5 years
DefinedBenefitPlanAssumptionsUsedToDetermineBenefitObligationsRateofCompensationIncreaseMinimum	3.50%	3.60%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate		3.05%
DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostRateOfCompensationIncreaseMaximum	5.00%	5.00%	3.90%
DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostRateOfCompensationIncreaseMinimum	3.60%	3.10%	3.10%
DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostDiscountRateAfterRemeasurement		4.55%
Defined Benefit Plan, Plan Assets, Expected Long-Term Rate-of-Return, Description	We determine our discount rates annually. We estimate our discount rate based upon a comparison of the expected cash flows associated with our future payments under our defined benefit pension and other postemployment obligations to a hypothetical bond portfolio created using high-quality bonds that closely match expected cash flows. Bond portfolios are developed by selecting a bond for each of the next 60 years based on the maturity dates of the bonds. Bonds selected to be included in the portfolios are only those rated by Moody’s as AA- or better and exclude callable bonds, bonds with less than a minimum issue size, yield outliers and other filtering criteria to remove unsuitable bonds.
Regulatory assets, Noncurrent	$ 287,906,000	$ 330,831,000
Employee benefit obligations	20,265,000	19,587,000
AdjustmentToPensionExpenseDueToRemeasurement				$ 7,200,000
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax	478,000	(5,823,000)	$ (1,250,000)
Regulatory Assets	$ 363,214,000	$ 606,403,000
Defined Benefit Plan, Health Care Cost Trend Rate Assumed, Next Fiscal Year	6.00%	6.50%
Defined Benefit Plan, Year Health Care Cost Trend Rate Reaches Ultimate Trend Rate	2030	2030
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	100.00%
Defined Contribution Plan, Employer Discretionary Contribution Amount	$ 12,600,000	$ 10,900,000	9,900,000
Ultimate Trend Rate, Current Year
Components of net periodic benefit cost:
Defined Benefit Plan, Ultimate Health Care Cost Trend Rate	4.50%
Ultimate Trend Rate, Prior Year
Components of net periodic benefit cost:
Defined Benefit Plan, Ultimate Health Care Cost Trend Rate		4.50%
Grosvenor Registered Multi Limited Partnership
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	$ 40,872,000	$ 40,160,000
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Unfunded Commitments	$ 0	$ 0
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investment Redemption, Frequency	quarterly	quarterly
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investment Redemption, Description	65	65
K2 Institutional Investors I I Limited Partnership
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	$ 48,254,000	$ 46,871,000
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Unfunded Commitments	$ 0	$ 0
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investment Redemption, Frequency	quarterly	quarterly
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investment Redemption, Description	91	91
Investment grade bonds
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	70.00%
US Large Cap Equity
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	13.00%
Alternative Investments
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	7.00%
Developed Foreign Large Cap Equities
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	5.00%
Mid Cap Equities
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	3.00%
Emerging Market Equities
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	1.00%
Small Cap Equities
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	1.00%
Fixed Income Funds
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Investment Policy and Strategy, Description	90 percent
Equity Securities
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Investment Policy and Strategy, Description	10 percent
Nonservice Costs Member
Components of net periodic benefit cost:
Regulatory assets, Noncurrent	$ 2,200,000	$ 2,800,000
ONE Gas Pension Plans [Member]
Components of net periodic benefit cost:
Service cost	7,242,000	10,369,000	13,811,000
Interest cost	42,428,000	36,150,000	29,458,000
Defined Benefit Plan, Benefit Obligation, Contributions by Plan Participant	0	0
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	23,015,000	(259,261,000)
Defined Benefit Plan, Benefit Obligation, Benefits Paid	(53,713,000)	(55,326,000)
Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Plan Amendment	0	2,711,000
Expected return on assets	(59,518,000)	(58,528,000)	(62,382,000)
Amortization of unrecognized prior service cost	372,000	248,000	0
Amortization of net (gain) loss	2,008,000	16,793,000	45,523,000
Net periodic benefit cost	$ (7,468,000)	$ 5,032,000	$ 26,410,000
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate	5.30%	5.60%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate	5.60%		2.80%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-Term Rate of Return on Plan Assets	6.75%	6.40%	7.15%
Defined Benefit Plan, Benefit Obligation	$ 803,605,000	$ 784,633,000	$ 1,049,990,000
Defined Benefit Plan, Plan Assets, Amount	795,381,000	768,961,000	1,013,244,000
Defined Benefit Plan, Funded (Unfunded) Status of Plan	(8,224,000)	(15,672,000)
Assets for Plan Benefits, Defined Benefit Plan	13,409,000	5,267,000
Liability, Defined Benefit Plan, Current	(1,368,000)	(1,352,000)
Employee benefit obligations	(20,265,000)	(19,587,000)
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position	(8,224,000)	(15,672,000)
Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss)	78,827,000	(190,484,000)
Defined Benefit Plan, Plan Assets, Contributions by Employer	1,306,000	1,527,000
Defined Benefit Plan, Plan Assets, Contributions by Plan Participant	0	0
Defined Benefit Plan, Plan Assets, Benefits Paid	(53,713,000)	(55,326,000)
Defined Benefit Plan, Accumulated Benefit Obligation	772,100,000	746,800,000
Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year	1,400,000
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, before Tax	(619,000)	7,369,000	67,000
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, before Tax	1,000	159,000	1,562,000
Increase (Decrease) in Deferred Income Taxes	140,000	(1,705,000)	(379,000)
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax	(478,000)	5,823,000	1,250,000
Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, Prior Service Cost (Credit), before Tax	(2,091,000)	(2,463,000)
Defined Benefit Plan, Accumulated Other Comprehensive Income (Loss), Gain (Loss), before Tax	(246,988,000)	(245,290,000)
DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeLossBeforeRegulatoryAssetsAndTaxes	(249,079,000)	(247,753,000)
Regulatory Assets	247,684,000	246,975,000
Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, before Tax	(1,395,000)	(778,000)
Deferred Tax Liabilities, Regulatory Assets	213,000	74,000
Accumulated Other Comprehensive (Income) Loss, Defined Benefit Plan, after Tax	(1,182,000)	(704,000)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	101,476,000	101,511,000	108,757,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Period Increase (Decrease)	2,095,000	1,467,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	1,562,000	3,215,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	(3,074,000)	(4,470,000)
FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPeriodDecrease	(618,000)	(7,458,000)
Defined Benefit Plan, Expected Future Benefit Payment, Year One	55,391,000
Defined Benefit Plan, Expected Future Benefit Payment, Year Two	55,988,000
Defined Benefit Plan, Expected Future Benefit Payment, Year Three	56,422,000
Defined Benefit Plan, Expected Future Benefit Payment, Year Four	56,591,000
Defined Benefit Plan, Expected Future Benefit Payment, Year Five	57,296,000
Defined Benefit Plan, Expected Future Benefit Payment, after Year Five for Next Five Years	286,471,000
ONE Gas Pension Plans [Member] | Fair Value, Inputs, Level 1 [Member]
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	93,777,000	154,493,000
ONE Gas Pension Plans [Member] | Fair Value, Inputs, Level 2 [Member]
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	600,128,000	512,957,000
ONE Gas Pension Plans [Member] | Fair Value, Inputs, Level 3
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	101,476,000	101,511,000
ONE Gas Pension Plans [Member] | Equity Securities
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	88,477,000	150,027,000
ONE Gas Pension Plans [Member] | Equity Securities | Fair Value, Inputs, Level 1 [Member]
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	88,477,000	150,027,000
ONE Gas Pension Plans [Member] | Equity Securities | Fair Value, Inputs, Level 2 [Member]
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	0	0
ONE Gas Pension Plans [Member] | Equity Securities | Fair Value, Inputs, Level 3
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	0	0
ONE Gas Pension Plans [Member] | Government Obligations
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	204,669,000	160,799,000
ONE Gas Pension Plans [Member] | Government Obligations | Fair Value, Inputs, Level 1 [Member]
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	0	0
ONE Gas Pension Plans [Member] | Government Obligations | Fair Value, Inputs, Level 2 [Member]
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	204,669,000	160,799,000
ONE Gas Pension Plans [Member] | Government Obligations | Fair Value, Inputs, Level 3
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	0	0
ONE Gas Pension Plans [Member] | Corporate Obligations
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	366,482,000	329,973,000
ONE Gas Pension Plans [Member] | Corporate Obligations | Fair Value, Inputs, Level 1 [Member]
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	0	0
ONE Gas Pension Plans [Member] | Corporate Obligations | Fair Value, Inputs, Level 2 [Member]
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	366,482,000	329,973,000
ONE Gas Pension Plans [Member] | Corporate Obligations | Fair Value, Inputs, Level 3
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	0	0
ONE Gas Pension Plans [Member] | Cashand Money Market Funds
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	34,277,000	26,651,000
ONE Gas Pension Plans [Member] | Cashand Money Market Funds | Fair Value, Inputs, Level 1 [Member]
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	5,300,000	4,466,000
ONE Gas Pension Plans [Member] | Cashand Money Market Funds | Fair Value, Inputs, Level 2 [Member]
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	28,977,000	22,185,000
ONE Gas Pension Plans [Member] | Cashand Money Market Funds | Fair Value, Inputs, Level 3
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	0	0
ONE Gas Pension Plans [Member] | Insurance Contracts and Group Annuity Contracts
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	12,350,000	14,480,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	12,350,000	14,480,000	17,301,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Period Increase (Decrease)	0	1,467,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	1,562,000	182,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	(3,074,000)	(4,470,000)
FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPeriodDecrease	(618,000)	0
ONE Gas Pension Plans [Member] | Insurance Contracts and Group Annuity Contracts | Fair Value, Inputs, Level 1 [Member]
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	0	0
ONE Gas Pension Plans [Member] | Insurance Contracts and Group Annuity Contracts | Fair Value, Inputs, Level 2 [Member]
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	0	0
ONE Gas Pension Plans [Member] | Insurance Contracts and Group Annuity Contracts | Fair Value, Inputs, Level 3
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	12,350,000	14,480,000
ONE Gas Pension Plans [Member] | Other Investments
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	89,126,000	87,031,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	89,126,000	87,031,000	91,456,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Period Increase (Decrease)	2,095,000	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	0	3,033,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	0	0
FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPeriodDecrease	0	(7,458,000)
ONE Gas Pension Plans [Member] | Other Investments | Fair Value, Inputs, Level 1 [Member]
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	0	0
ONE Gas Pension Plans [Member] | Other Investments | Fair Value, Inputs, Level 2 [Member]
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	0	0
ONE Gas Pension Plans [Member] | Other Investments | Fair Value, Inputs, Level 3
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	89,126,000	87,031,000
ONE Gas Postretirement Benefit Plans [Member]
Components of net periodic benefit cost:
Service cost	730,000	1,274,000	1,587,000
Interest cost	9,154,000	6,448,000	6,251,000
Defined Benefit Plan, Benefit Obligation, Contributions by Plan Participant	2,823,000	3,035,000
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	(5,551,000)	(48,609,000)
Defined Benefit Plan, Benefit Obligation, Benefits Paid	(16,963,000)	(16,612,000)
Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Plan Amendment	0	0
Expected return on assets	(9,728,000)	(13,181,000)	(16,807,000)
Amortization of unrecognized prior service cost	153,000	41,000	(279,000)
Amortization of net (gain) loss	(48,000)	217,000	373,000
Net periodic benefit cost	$ 261,000	$ (5,201,000)	$ (8,875,000)
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate	5.40%	5.70%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate	5.70%	3.00%	2.70%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-Term Rate of Return on Plan Assets	5.55%	5.85%	7.50%
Defined Benefit Plan, Benefit Obligation	$ 158,535,000	$ 168,342,000	$ 222,806,000
Defined Benefit Plan, Plan Assets, Amount	181,608,000	181,877,000	231,994,000
Defined Benefit Plan, Funded (Unfunded) Status of Plan	23,073,000	13,535,000
Assets for Plan Benefits, Defined Benefit Plan	23,073,000	13,535,000
Liability, Defined Benefit Plan, Current	0	0
Employee benefit obligations	0	0
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position	23,073,000	13,535,000
Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss)	11,325,000	(38,432,000)
Defined Benefit Plan, Plan Assets, Contributions by Employer	2,546,000	1,892,000
Defined Benefit Plan, Plan Assets, Contributions by Plan Participant	2,823,000	3,035,000
Defined Benefit Plan, Plan Assets, Benefits Paid	(16,963,000)	(16,612,000)
Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year	0
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), after Reclassification Adjustment, before Tax	0	0	0
Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, Prior Service Cost (Credit), before Tax	0	(153,000)
Defined Benefit Plan, Accumulated Other Comprehensive Income (Loss), Gain (Loss), before Tax	(1,457)	(8,557,000)
DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeLossBeforeRegulatoryAssetsAndTaxes	(1,457)	(8,710,000)
Regulatory Assets	1,457	8,710,000
Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, before Tax	0	0
Defined Benefit Plan, Expected Future Benefit Payment, Year One	14,127,000
Defined Benefit Plan, Expected Future Benefit Payment, Year Two	13,890,000
Defined Benefit Plan, Expected Future Benefit Payment, Year Three	13,505,000
Defined Benefit Plan, Expected Future Benefit Payment, Year Four	13,194,000
Defined Benefit Plan, Expected Future Benefit Payment, Year Five	12,848,000
Defined Benefit Plan, Expected Future Benefit Payment, after Year Five for Next Five Years	59,299,000
ONE Gas Postretirement Benefit Plans [Member] | Equity Securities
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	7,031,000	5,983,000
ONE Gas Postretirement Benefit Plans [Member] | Equity Securities | Fair Value, Inputs, Level 1 [Member]
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	7,031,000	5,983,000
ONE Gas Postretirement Benefit Plans [Member] | Equity Securities | Fair Value, Inputs, Level 2 [Member]
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	0	0
ONE Gas Postretirement Benefit Plans [Member] | Equity Securities | Fair Value, Inputs, Level 3
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	0	0
ONE Gas Postretirement Benefit Plans [Member] | Government Obligations
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	41,863,000	43,291,000
ONE Gas Postretirement Benefit Plans [Member] | Government Obligations | Fair Value, Inputs, Level 1 [Member]
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	0	0
ONE Gas Postretirement Benefit Plans [Member] | Government Obligations | Fair Value, Inputs, Level 2 [Member]
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	41,863,000	43,291,000
ONE Gas Postretirement Benefit Plans [Member] | Government Obligations | Fair Value, Inputs, Level 3
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	0	0
ONE Gas Postretirement Benefit Plans [Member] | Corporate Obligations
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	38,615,000	38,095,000
ONE Gas Postretirement Benefit Plans [Member] | Corporate Obligations | Fair Value, Inputs, Level 1 [Member]
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	0	0
ONE Gas Postretirement Benefit Plans [Member] | Corporate Obligations | Fair Value, Inputs, Level 2 [Member]
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	38,615,000	38,095,000
ONE Gas Postretirement Benefit Plans [Member] | Corporate Obligations | Fair Value, Inputs, Level 3
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	0	0
ONE Gas Postretirement Benefit Plans [Member] | Cashand Money Market Funds
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	13,996,000	8,371,000
ONE Gas Postretirement Benefit Plans [Member] | Cashand Money Market Funds | Fair Value, Inputs, Level 1 [Member]
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	751,000	750,000
ONE Gas Postretirement Benefit Plans [Member] | Cashand Money Market Funds | Fair Value, Inputs, Level 2 [Member]
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	13,245,000	7,621,000
ONE Gas Postretirement Benefit Plans [Member] | Cashand Money Market Funds | Fair Value, Inputs, Level 3
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	0	0
ONE Gas Postretirement Benefit Plans [Member] | Insurance Contracts and Group Annuity Contracts
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	80,102,000	86,137,000
ONE Gas Postretirement Benefit Plans [Member] | Insurance Contracts and Group Annuity Contracts | Fair Value, Inputs, Level 1 [Member]
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	0	0
ONE Gas Postretirement Benefit Plans [Member] | Insurance Contracts and Group Annuity Contracts | Fair Value, Inputs, Level 2 [Member]
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	80,102,000	86,137,000
ONE Gas Postretirement Benefit Plans [Member] | Insurance Contracts and Group Annuity Contracts | Fair Value, Inputs, Level 3
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	0	0
ONE Gas Postretirement Benefit Plans [Member] | Other Investments
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	181,607,000	181,877,000
ONE Gas Postretirement Benefit Plans [Member] | Other Investments | Fair Value, Inputs, Level 1 [Member]
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	7,782,000	6,733,000
ONE Gas Postretirement Benefit Plans [Member] | Other Investments | Fair Value, Inputs, Level 2 [Member]
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	173,825,000	175,144,000
ONE Gas Postretirement Benefit Plans [Member] | Other Investments | Fair Value, Inputs, Level 3
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	$ 0	0
401k Plan
Components of net periodic benefit cost:
Defined Contribution Plan, Employer Matching Contribution, Percent of Match	100.00%
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay	6.00%
Defined Contribution Plan, Cost	$ 16,700,000	$ 15,300,000	$ 14,300,000